1. Field of the Invention
The present invention relates to a technique for preventing a side erase in a magnetic disk apparatus.
2. Description of the Related Art
A magnetic disk apparatus is constituted by a magnetic head, a rotating magnetic disk, a motor for driving the magnetic head and magnetic disk, and a circuit for controlling the motor. Such a disk apparatus records information on the magnetic disk (magnetic medium) by magnetizing the surface of the magnetic disk using a magnetic field generated by the magnetic head.
In recent years, a small-sized magnetic head has been adopted in such a magnetic disk apparatus in order to achieve higher density information recording. As a result, tracks to be magnetized are arranged at high density on the magnetic disk.
However, the higher density arrangement inevitably makes the distance between adjacent tracks smaller. This causes a side erase phenomenon in which the magnetic information of tracks (tracks T+1 and T−1 in FIG. 13) on both sides of a write target track (track T in FIG. 13) become weak by a leak magnetic field from the magnetic head. For example, in the case where data has been written to a given track a number of times and where no data has been written to tracks on both sides of the given track, the magnetic information of the tracks on both sides become weak to such a degree that it cannot be read out correctly, resulting in loss of information.
To cope with such a problem, there is known a technique that counts the number of times of data write operation for track. Further, there is known a technique that reads track data that is likely to be erased by the side erase phenomenon and writes the read out data to the same track (refer to, e.g., Patent Document 1: Jpn. Pat. Appln. Laid-Open Publication No. 2007-242207).